Obstacles to regulation
If your dog or cat's blood glucose levels remain high over a long time, or appear to alternate between high and low without logic, even though it's getting enough insulin, one or more of the following problems may apply: In unregulated animals :* High-carb cat/dog food: Many commercial foods (especially "Light" foods) are extremely high in cereals and therefore carbohydrates. The extra carbohydrates will keep the cat or dog's blood sugar high, and if you're free-feeding may also make the blood sugar curve over the course of the day unpredictable. In general, canned foods are lower in carbohydrates than dry ones, and canned "kitten" foods lower still. See Low-Carb diet for more information on how to lower your pet's carbs. :*'Infection': Any infection in the body, including dental, urinary, kidney, colds, and even hidden infections, will often cause stubborn high blood glucose levels. Ask your vet to check for the possibility of infection if dosage and diet don't seem to be bringing sugar levels down. :* Insulin resistance from glucose toxicity: after a few days of continually high blood glucose (as often happens when first diagnosed), the animal may have "burnt" some of the body cells due to the oxidizing effects of the glucose the tissues are being bathed with. These damaged cells may at first be unable to effectively absorb even an ideal dose of insulin in their usual way, which leads to more high glucose. Consult a veterinarian about this possibility -- some of the recommended ways to break this cycle are unsafe to try without veterinary supervision. :* Chronic overdose masked by Somogyi: A dose that is fractionally too high can easily cause a Somogyi rebound, which causes hyperglycemia and can look like a need for more insulin. This condition can continue for days or weeks, and it's very hard on the cat's metabolism. Especially since you're likely to keep raising the dosage to compensate, making things worse. :* Wrong insulin: Different brands and types of insulin have idiosyncratic effects on different cats and dogs. If you've settled on a dose that seems to keep the pet's blood sugar within range at peak effectiveness, but the sugar readings remain dangerously high at shot times, the insulin may not be lasting long enough for your pet, or may not be the best choice. Switching to a slower-acting or a better-tolerated insulin for that pet, and lowering the dose initially to be safe, may be the next step. In previously-regulated animals Certain things can cause a previously well-regulated cat or dog to suddenly experience hyperglycemia too: :* Illness: Colds, viruses, and other temporary illnesses and infections, even hidden ones, can push blood sugar high for a while. Other medical stresses can lead to Insulin resistance too. :* Medications: Certain medications for other conditions (including heartworm and flea medications), may cause dogs' or cats' blood sugar to skyrocket temporarily. Interceptor (Novartis) carries no advisory regarding these possibilities for both dogs and cats, nor do other comparable medications. Hormones and steroids can also contribute to non-regulation or loss of regulation. All females should be spayed as the hormones released in their menstrual cycles drive blood glucose up. Some revert to non-diabetic status after being spayed. Steroid use can also produce a temporary, transient diabetes which often disappears after discontinuing use of steroids. :*'Antibodies': Antibodies can be created against the insulin itself or even its suspension. Both NPH/Isophane and PZI insulins use protamine (protein derived from salmon) to do this. So it is then possible for the insulin itself not to be rejected, with the reactivity being to the protamine of the suspension. Antibodies This type of insulin resistance is defined as loss of 70%+ of injected insulin to antibody binding. It is considered rare but possible. Reactions are also possible from the preservatives which are necessary to all insulins. They do differ from suspension to suspension, however. Case of a human who was sensitive to the preservatives in NPH/isophane, but not Lente, as they differ. :* Damaged Insulin: Insulin that is getting too old, or has been dropped or shaken or mishandled, or exposed to a lot of light or heat, will be less effective than before. Check for discoloration or floating objects in the insulin -- it may also be contaminated. It's also possible that the new or newer vial from the pharmacy may be flawed. If you've recently started it and are having problems, this might be the case. Taking down the lot number and getting a new vial that has a different batch/lot number should take care of this. Don't be in a hurry to discard the "old" vial of insulin you were using. If your insulin is one that needs to be ordered, the old vial is all you have until the order comes in. It can be potent enough to see you through until you get your new one. If there's nothing wrong with the old vial except that it's begun to lose potency, don't be afraid to go back to it if something seems not right about your new vial. Keeping your old vial until you're certain all's going well with using the new one is a good idea. Insulin that is not properly rolled before shooting can become weaker or stronger over a period of time, leading either to high blood sugar or overdosing and possible Somogyi rebound. :* Reduced insulin need: Sometimes your pet will suddenly appear to need less insulin than before. If this happens (their blood sugar will go lower than usual one day), drop the dose immediately and call your vet. If testing just before an injection, and the reading is much lower than expected, it may be wisest to skip that dose and continue retesting every 2-3 hours. If the drop is dramatic and leads to a hypglycemic episode(see below), the cat's sensitivity to insulin may increase dramatically. You should consider dropping their dose after consulting your veterinarian, and raise it only by half to one unit per 5-7 days, as before. Reduced need can happen because of recovery from glucose toxicity, or because a cat is on the way to remission, or for other reasons. It's rare for a diabetic dog to begin producing insulin again; it is possible from having pancreatitis. Diabetes with rebound hyperglycemia. :* Rebound due to single overdose: Sometimes your pet's blood sugar will suddenly seem much higher than usual. This is often not a good time to increase their insulin dosage -- quite the opposite. It may instead be another case of "reduced need". It often indicates that a low blood sugar condition (or rapid sugar drop) was experienced a few hours before, and a Somogyi rebound is in progress. To be sure, drop the next dose by 15%-50% and take glucose readings every 4 to 8 hours until the glucose levels out. Then wait a day or two for the Somogyi hormones to decrease in the body, and then you can increase again by 0.5-unit steps every 5-7 days. If you experienced this rebound, chances are that your original dose was too high, or the pets' insulin requirements decreased, so you should try to find an ideal dose at a lower point. External Links *Why previously-regulated cats lose control, by Richard Nelson, DVM *Regulation section of the FDMB FAQ *The Difficult Diabetic *Treating the Complicated Diabetic Patient *The Hard to Regulate Diabetic Pet *Dr. Richard Nelson's NAVC 2001 presentation re: ineffectiveness of insulin. *Temporary immune-realted canine diabetes case abstract. *Unstable Diabetics: Solving the Problems Category:RegulationCategory:Tips